Office workers have more flexibility in time but should be more vigilant to avoid falling into comfort zone that affects work efficiency.

I do not believe it when one says it does not matter he always is late to work and takes much working time to do personal things as long as he can deliver result.
I believe he can deliver more results if he can have more discipline.

I am not going to describe more about things that are already written in common company rules for example doing part-time job during office hours.
Even worse if you distract your colleague by selling things to them.
You should already know it is a matter of code of conduct besides affecting your efficiency.
Please note that this article is also not applicable for people who work at home.

Tips

At night before sleep prepare the things to bring and to wear to work the next morning.
Go to bed immediately when you are already sleepy so that you are not tired for work.
There is nothing you cannot wait until the next early morning that you must compromise to delay bed time.

In the next morning have breakfast, go to toilet etc before working hours.
It is better to go to toilet at home just in case there is water supply hiccup in the company (unlucky day...).

Groom up yourself so that you are confident to work with colleagues.

Start working when working hours start.
If you still do personal things when the work hours start, you will lose work momentum for the rest of the day.
More on this later.

Remove the clutter on your work place.
Clean and tidy desk (including computer screen etc) prepares your mindset to work.
Do not accumulate task on work desk.
Clear away items that are not useful, e.g. if you already have one stapler, then any extra stapler is not useful.
One's work performance can be doubted if the work desk is a mess.

Sit up straight.
Do things fast.
Talk clearly.
These will also prevent you from becoming drowsy.
If you still become drowsy, take a walk (e.g. go to pantry to drink some water or go to toilet to wash face).
When you want to say something to your colleague, rise and look for him.
Do not use email to do that.
Long-hour sitting can affect mental sharpness.

Choosing email pop-up alert is personal preference.
The more important thing is to see who the sender is and what the subject is before opening the new email.
Do not open it if you are not ready to act on it yet.
After acting on it, save as PDF as necessary and delete the email.
It is better to have clean inbox that does not need to scroll.

Do not do personal things during work hours.
Do not do it even for a minute.
This is cheating.
You can get side-tracked for a significant amount of time.
Personal matters can only be done during work if it cannot be done after work (for example calling a lawyer who has the same working time as yours).
Do not check private email during work.
Without realizing it, it can take one hour or more although you have intended a few minutes during a coffee break.
Internet connection at home is necessary if you are a regular Internet surfer.

Write down immediately personal matters that appear in your mind in a private to-do list so that they do not continuously bug your mind.
Do the personal things after work.
By writing down the to-do, you can be sure that it is important because you will not go through the hassle of writing unimportant things down.
This to-do list is temporary and you can name it as "To Do Tonight", "To Do Tomorrow Night" or "To Do This Weekend" depending on your schedule.
The other benefit of having this list is you will not forget about the things that you should do tonight.

Even if you are out of work idea for moment and you need to finish it, do not engage other matters (including personal ones).
It is better to sit there without work progress rather than doing other things.
That boring period will push you more to jump out of idleness to finish the task.

Finish the things at one go.
If you leave the current task for another thing, you will spend even more time next time to reorganize the things when you come back to it.
This is the cost of poor quality (COPQ) for switching task.
Also you will still remember the unfinished task while you are doing the another thing and stress out.
It is better to do one task excellently than to do a few tasks with moderate result.
Finish one thing first before proceeding to another.
Doing many things is equal to doing nothing.
You should say no to your boss if he interrupts you with more task while you still have unfinished task at hand that you are working on non-stop.

Before doing the anything that pops up in mind, analyze in mind whether it is important or not.
Ignore if it is unimportant.
Write any task down before performing it, regardless whether you are able to solve it immediately or not.
This will make sure you do not forget any task if you are distracted with other task that others request you to do.
This list is also important for the company in case if you are not around and other people need to know what needs to be done.
Even you can build up this work culture in the company by asking the person who will do the task to write down the task in his to-do list in front of you before leaving his desk.

Finish the task given by the superior first.
It is usually more urgent.
Tell the superior what you are doing when the task is given to you to let him or her decide which one is more urgent.

Avoid listening to songs because the lyric may make you lose focus.
Music is OK but use earphone so that you will not bring down other people's efficiency that do not like distraction in office.

You may turn on private instant messenger to provide a way for other people to reach you but do not initiate any chat during working hours.
Turn off the alert when a contact comes online.
This is like turning on private handphone.
Please check your company policy for this one.
In some companies, this messenger is blocked by proxy server.

You may reply private SMS you get during working hours in your handheld device as long as you do not always get private SMS during work.

Control your temper at work.
Losing composure does not only affect your own work efficiency, but also distracts your colleagues.
And later you will have more difficulties working with the person you have shouted at.
On the other hand, if your colleague shouts at you when other people are around (such as in a meeting), please do not shout back but continue what you have to say about work calmly.
The boss will not want to promote people who constantly engage in conflicts.

There are times when you still feel like working during lunch time.
That is not good.
Have a clear line.
Do something else.
Have a chat with people during lunch or something.

Do not have heavy meal at work desk.
Work desk is a place to work.
Make the mindset correct and you will be more focused at work.
Snacks and fruits are OK provided that
a) you can hold it with one hand.
b) it will not dirty the workplace.
c) it can be eaten up quickly.

Also never open websites unrelated to work or read books and magazines unrelated to work at workplace even if it is off working hours.
Workplace is for work.
If you want to have a chat on something unrelated to work with your colleagues, go to the pantry.
Same things apply for private phone call.

Leave when the work hours end.
Staying back may mean that you are inefficient and will give you more stress in life because there is no clear boundaries between work and personal life.
Once in a while if you really have urgent work matters to do, do not bring the work home but finish it before leaving.
Think of the workplace as a place that you earn money so you do not want to do something that cannot earn money there.

If you are unsatisfied with your salary, openly talk to your superior about it in the office.
If it is unsuccessful, then be open to the opportunity to move on to another company.
Do not whine to others except your superior about the salary because they cannot do anything.
Work quality must not be affected by emotion resulted from the remuneration and benefit.
Be professional.

Your efficiency should not be affected by the negative comment from your boss.
In a company anybody will receive negative comment if his performance is not good.
We should have no hard feeling.
It is not personal attack.
If you know you have idle time in the company and your colleagues know that, then admit the blame from the boss openly and seek for improvement.
If you are all the time busy but you are still blamed of not doing something, then talk to the boss openly.
Tell him that are sitting around being idle but instead you are busy on some other important matters that he has also asked you to do.
If the boss is not understanding, then move to other company without further ado.
Again, be professional.

Exercise regularly to maintain health.
Healthy body gives you a sharp mind at work.
I think the company should make this compulsory if it wants employees with good performance.
No company wants their workers who are always on sick leave.
Also no worker likes their coworkers to be always under the weather.